There are so-called "economizer" systems currently available on the market which deliver air from outside a building to the interior thereof. Prior art systems of this nature, however, suffer from certain deficiencies. For example, conventional prior art systems sense only outdoor air temperatures. For this reason, the prior art arrangements cannot use outside air for cooling if the outside air is warmer than the set point of the control employed in the system, even if it is much cooler outside than the air temperature within the interior of the building.
In addition, these prior art arrangements do not lend themselves for use in combination with mechanical cooling devices, being employed in lieu of air conditioners or other mechanical cooling means.
Because of these limitations, conventional "economizer" systems do not utilize outside air for building cooling as frequently as one might wish. This results in energy waste, unnecessary and expensive utilization of air conditioners or other mechanical cooling devices or, in some cases, needless discomfort to the occupants of the building.
U.S. Pat. No. 4,915,294, issued Apr. 10, 1990 to Calvin R. Wylie, discloses a system for lessening the temperature differential between the upper and lower levels of a building including sensing means for sensing the temperatures of both of the levels, air delivery means for delivering air between the level interiors, and control means for activating the air delivery means when a temperature differential of a predetermined magnitude is sensed by the sensing means. The system disclosed in such patent is not applicable for cooling a building interior through the use of outside air.